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I need to install Windows 7 x64 over the existing OS (unwanted factory issued Win8, for which I've already made restore media for) on a Dell XPS 15 (L521x). It needs to use UEFI boot and use the 128GB mSATA drive to cache a 1TB 5400rpm HDD using Intel Rapid Storage Technology (RST).

Getting this wrong leads to various forms of locking up at the Windows boot logo, or the Windows installer claiming "Windows can not install on this hardware", or infinite reboot cycles.

Does anyone have a method for this?

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up vote 2 down vote accepted

Ok, I did it already...


Some form of Windows 7 x64 full install media will be required, but not a Windows 7 upgrade disc as they don't reliably boot UEFI.

Down load the latest Intel Rapid Storage Technology driver F6 floppy installer for Win7 x64 usually named Unzip this onto a USB stick as it will be needed during the Win7 install.


Boot into the BIOS setup (F2 on the Dell XPS 15, often Del on other systems, read your manual) and check the following settings:

  • That the SATA controller is in RAID or Intel Rapid Storage Technology mode
  • That Secure boot is disabled, this is only supported by Windows 8
  • That Legacy boot mode is enabled
  • That UEFI boot mode is also available

Note: When booting always use UEFI boot options and not the Legacy options. The Win7 install disc should boot with UEFI, but doesn't do it reliably without the Legacy option enabled.

Clean and Destroy

This is destructive and will wipe the hard drives

You need a Win-PE DOS command prompt, boot your computer and activate your boot menu (F12 for the Dell XPS 15) and UEFI boot the Win7 install disk and choose Repair. Jump through whatever hoops it asks until you can open a Command Prompt.

In the command prompt run through the following commands (relevant to the Dell XPS 15, your computer may vary the required disk numbers):

list disk
select disk 0
select disk 1

Return to the Win7 install menu by clicking the little red X at the top right of the repair tools menu, or reboot off your disc.

Install Windows 7

A custom install is required, two things need to be done:

  1. Use the Advanced tools to select the large hard drive for the Windows install. Windows will insist on three partitions for UEFI, if you don't see three partitions UEFI is not set correctly. Either, the BIOS is not set correctly, or you chose to legacy boot your install media. Do nothing with the mSATA drive.

  2. Load the Intel Rapid Storage Technology drivers! Select the Drivers option and browse to the files from unzipped to a USB stick earlier. This stops the "Windows can not install on this hardware" issue mentioned earlier.

Install Windows, you know how you like it. Install all the drivers, except the Intel Rapid Storage Technology driver and application. Install Win7 SP1, you'll need windows6.1-KB976932-X64.exe. Run Windows update until it stops whining.

Now install the latest Intel Rapid Storage Technology application, the file named iata_enu.exe

After rebooting until the driver installs and Windows updates are satisfied, open the Intel Rapid Storage Technology application. There should be an Accelleration icon, use this to set up as large a cache on the mSATA SSD as you'd like (I chose 60GB), but do not use the Maximised option, it seems to cause trouble. Again with the rebooting.

Windows 7 should now be installed to boot UEFI and using Intel RST.

Note: You may be able to go back into the BIOS and disable Legacy boot, but this may render some systems unbootable.

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I think this should work with most systems with Series 7 Chipsets like the HM77 and Z77. – Aethylred Dec 23 '12 at 11:32
A side note, I was completely unable to make Windows 7 UEFI boot off a USB stick. Worked with Ubuntu, but could not make it happen with Windows 7 Enterprise 64-bit edition. – Aethylred May 2 '13 at 21:58

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